This invention relates to a method and apparatus for dry powder particle coating of work pieces and for converting a standard wet paint spray booth into a dry powder spray booth assembly. More particularly, this invention relates to a mobile compartment, having dry powder filters and screens mounted therein above powder collecting trays, that can be positioned in front of a standard wet paint spray booth to permit spraying of a dry plastic powder material on a workpiece positioned in front of the compartment.
Manufacturing processes today require the finishing of product with a protective and decorative coating. These coatings can take the form of plating, painting, or plastic coating, depending on the particular finish system employed. One of the methods of coating an article is to apply a dry plastic powder by spraying the powder on an object that has been pre-heated or electrostatically charged to attract the powder and cause it to be retained on the article until the article can be baked to melt and fuse the powder to the article. The advantages of this dry powder method of coating a product over the conventional painting or plating coating systems is that the plastic powders are 100% solids and have no solvent vehicles that evaporate during the drying process thereby causing pollution, fire and explosion hazards. While the dry powder system has many advantages, there are still many applications where a wet paint system must be used. Accordingly, most custom coating companies, paint shops and the like, must maintain a wet spray paint booth with suitable exhaust and pollution equipment. Since this equipment must be optimized for the capture of the solvents and liquid overspray, the systems are not ideally suited to capture plastic particles that may be oversprayed in the solid plastic particle systems. The solid plastic particles that miss the object to be painted impinge on the filter in a basically undamaged condition and can be collected and reused. It is therefore advantageous to have a spray booth system that not only prevents discharge of powder particles with its consequent pollution hazard, but one that collects the "overspray" powder for reuse in the coating operation. Since many shops already have extensive wet spray booth installations, I have found it advantageous to be able to provide a mobile auxiliary compartment that allows the instantaneous conversion of the wet spray booth to a dry powder spray booth by simply wheeling a dry powder compartment into place in front of a wet paint spray booth and attaching it thereto in a sealed configuration for straight-through airflow from the ambient into the wet paint spray booth exhaust and pollution control system. The mobile compartment dry powder spray booth of the present invention also provides a capability for collecting powder overspray and reusing it on another product. By the provision of multiple dry powder booth units and/or multiple filters and collecting trays different colors can be accommodated.